Sunlight: Friend or Foe? The Vitamin D and Sunscreen Debate

Vitamin D is getting a lot of attention from the media lately, and is the new “hot” topic in medical circles. Many people are having their vitamin D levels tested and finding out they are low in this essential nutrient. But what exactly is Vitamin D and why should you care about your Vitamin D levels? How does sunscreen use contribute to being low in this important vitamin, and what can we do about it?

What is Vitamin D?

Vitamin D MetabolismI remember learning in elementary school about photosynthesis, how plants capture the light of the sun and turn it into energy.  But what my teacher didn’t tell me is that humans actually do something similar in creating Vitamin D!

Vitamin D is actually not a vitamin, but a hormone.  It is produced from exposure to sunlight.  UV light from the sun starts off a chemical reaction in our skin to produce a precursor to Vitamin D which, with the help of the liver and kidneys, turns into active Vitamin D that our bodies can use.

Why Vitamin D is important

Vitamin D was originally discovered in 1918 as necessary nutrient to prevent rickets.  In more modern times, it has become famous primarily for helping your body absorb calcium to keep bones strong.

However, in the past few years, there has been an explosion of research linking Vitamin D deficiency to a wide range of medical conditions ranging from osteoporosis, multiple sclerosis, heart disease, many different types of cancer, depression, rheumatoid arthritis, PCOS, influenza, prostate health, infertility, high blood pressure, diabetes, seasonal affective disorder, migraines, and more.  (Please contact us for specific references).

Widespread deficiency of Vitamin D

A study in May 2009 reported that more than one third of mothers and more than half of their infants are vitamin D-deficient at the time of birth (9). Many other studies as well as clinical experiences are showing this deficiency is widespread in many people and populations globally (10).  Why are so many people in so many different countries low in this hormone that our bodies makes on its own?

Natural sources of Vitamin D

Sources of Vitamin DYou can get Vitamin D from some fortified foods, as well as from many types of fish, some mushrooms, and egg yolk, but by far the best way to get enough Vitamin D is through sun exposure on our skin.

Recommendations vary from 15-30 minutes a day, with at least 30% of your skin surface exposed (some recommendations suggest your face and arms; other suggest you also need your legs exposed) in order to synthesize enough for optimal health.  Depending on your latitude, altitude, pollution levels, cloud cover, and skin color, you may need more sun exposure to generate the amount necessary for optimal health.

Your Sunscreen may be blocking the production of Vitamin D

As we mentioned in our previous article about safe sunscreen use, many natural and conventional health care practitioners are concerned that the push to always wear sunscreen and avoid the sun at all costs has helped contribute to many people having suboptimal Vitamin D levels.

Here’s the rub:  The same sunscreen you are wearing to prevent skin cancer is also blocking your body’s ability to make Vitamin D!  Our bodies require UV light to make Vitamin D, and sunscreens block out UV light.  Even the natural, environmentally friendly sunscreens we featured last month still block UV light!  A sunscreen with SPF of 8 blocks your ability to synthesize Vitamin D by 92.5%, and increasing to SPF 15 blocks nearly 99% of your ability to make Vitamin D (1,2,3,4)!

So what should we do?

How do we reconcile this information with the mantra of the past few years to always wear sunscreen on every inch of your body, every minute of every day?  Why is it that despite sunscreen use, skin cancer rates are still high?

There is some debate that because Vitamin D is being shown as a cancer-fighting hormone, that by blocking its production through sunscreen, we are inadvertently making skin cancer rates worse.  Compound this with the toxic chemicals found in some sunscreen products, and you may have a recipe for disaster.

But on the other side, there is plenty of evidence showing that sunscreen and reducing sunburns prevents skin cancer.  Sunscreen also makes it possible for us to enjoy beautiful summer days without having to suffer from burning, peeling, stinging sunburns for the next week!

There has to be a middle ground; as with all things, moderation may be the best course of action.  Unlimited sun exposure, and the flip side of never having any sun exposure, are both proving to have unintended consequences.

Our Naturopathic Recommendations:

  • Lewis-Family-Vitamin-D-DropsWhat we personally do is try to go outside daily (if possible) for 15-30 minutes with shorts and a t-shirt, exposing our arms and legs to the bright sun.
  • If we’re going to be out any longer then that, we put on a EWG-approved sunscreen to avoid those chemicals that might make skin cancer worse.
  • Finally, we take a daily Vitamin D supplement, especially during the winter months when sunlight is less available, to boost what is naturally being made by our bodies.
  • Finally, we try to have our Vitamin D levels checked at least once a year to know what our levels measure.
    • If you don’t know your Vitamin D levels, there is a simple blood test you can take to find out where you fall.  Because Vitamin D can be toxic in large doses, it’s always a good idea to know your levels before starting any high-dose supplementation.  Your doctor can order this test for you, or if you don’t have insurance or a doctor who will run it for you, you may wish to order it directly through If you are a current patient at LFNH, please contact us for ways to order this test with additional cost savings.
  • Although the published RDA for Vitamin D is technically 200-400 IU a day (8), many sources and research suggest that this number may be too low to maintain adequate Vitamin D levels.  We concur with the research and experts who are now recommending at least 1000 IU from diet or supplements every day, if not more (5,6).  Especially in the winter when you’re not getting much sun exposure anyway, or with our modern habit of sitting inside all day in front of a computer with no sun exposure, it’s not a bad idea to take a supplement.  Vitamin D supplements tend to be very affordable and simple to take.
  • If you choose to supplement, look for the D3 form, not D2.  You will also want to work with a high-quality company that doesn’t have additional binders or other contaminants in their product.  If you are looking for a good supplement, try our convenient drops (400 IU per drop).


  1. Holick MF.Vitamin D deficiency.N Engl J Med.2007;357:266-281.
  2. Matsuoka LY , Wortsman J , Hanifan N , et al.Chronic sunscreen use decreases circulating concentration of 25-hydroxyvitamin D.Arch Dermatol.1988;124:1802-1804.
  3. Matsuoka LY , Ide L , Wortsmen J , et al.Sunscreen suppress cutaneous vitamin D3 synthesis.J Clin Endocrinol Metab.1987;64:1165-1168.
  4. Robinson JK.Sun exposure, sun protection, and Vitamin D. JAMA.2005;294(12):1541-1545.
  5. Rebecca Wike Malone, Cathy Kessenich.  Vitamin D Deficiency: Implications Across the Lifespan.  Journal for Nurse Practitioners.  08/25/2008)
  6. Bischoff-Ferrari HA , Giovannuci E , Willett WC , et al.Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes.Am J Clin Nutr.2006;84:18-28.
  7. Glerup H , Mikkelson K , Poulsen L , et al.Commonly recommended daily intake of vitamin D is not sufficient if sunlight exposure is limited.J Intern Med.2000;247:260-268.
  9. Stein, Jill.  Vitamin D Deficiency Is Common in Mothers and Newborns.  Reuters Health Information, May 2009.
  10. Mithal A, Wahl DA, Bonjour JP, Burckhardt P, Dawson-Hughes B, Eisman JA, El-Hajj Fuleihan G, Josse RG, Lips P, Morales-Torres J; on behalf of the IOF Committee of Scientific Advisors (CSA) Nutrition Working Group.  Global vitamin D status and determinants of hypovitaminosis D. Osteoporos Int.  Jun 19, 2009.